The rocks look like they will go down if you give them a little stimulus and more than great backdrops for taking selfies. They can help determine the risk earthquakes in an area and whether it safe to build there. The good news is that the part of California where this strategy first applied is safer than previously thought, which is reassuring because there is already a nuclear power plant located there. In different parts of the world, one can find large rocks prepared in the earth below, usually after the soft surrounding elements have destroyed. Again, some left behind by glaciers that have warmed the world and retreated.
Either way, these objects, creatively known geologists as precisely balanced rocks (PBRs), can displaced by sufficiently strong earthquakes. Thus, Anna Rudd, a PhD student at Imperial College London, argued that their survival indicates any earthquake in the vicinity since the source of a PBR must have been smaller than the minimum magnitude earthquake to displace it. It turns out that one of the major problems in seismology is how to solve or at least improve – how a site can said to be at risk of major earthquakes and therefore how safe it is to build there. Although attempts have made to determine the risk of an earthquake based on the measurement of the physical characteristics of an error, it has not yet proven reliable.
Instead, the usual way is to use data on previous problems. Past performance may not be a guarantee of future results as the ads say, but it is often the best guide for us. Unfortunately, our seismic energy records are comfortable short-term, especially where written records are recent as a result. Rod turned around, finding evidence of the absence of a major earthquake in an area of Sandwich, California, between the Hosgri and Los Osos fault areas of the San Andres Fault.
“PBRs act like reverse earthquakes that contain a history of regional earthquakes that we haven’t seen, and we just tremble without exceeding the upper limit of past earthquakes,” Rodd said in a statement. Rod identified seven PBRs located at Double Rock in California as appropriate and modeled the forces needed to close their perches. He then used the ratio of beryllium in the surface layers of the PBR to determine how long the boulders met cosmic rays, when they lost the soft material covering that stopped them from moving at once.
In AGU Advances, Rod and co-authors use this data to determine that one earthquake per 10,000 or more years 27 percent less than previously estimated. Moreover, the uncertainty in this number has decreased by 49 percent. This does not diminish the likelihood of a major earthquake, such as placing somewhat larger damage in nearby cities before the end of 2020, but it does mean that the chances are smaller than previously thought. Useful information for insurance companies engineers who might otherwise be overbuild. This is also a relief for anyone concerned about the location of the Diablo Canyon nuclear power plant, which is located just above the coast from Double Rock.